Summary of Work: The Baltimore Longitudinal Study of Aging (BLSA), the NIAs major research program on human aging, has been conducted at the Gerontology Research Center since 1958. The study represents a consortium of scientists who work to characterize normal and pathological aging. The BLSA consists of a series of longitudinal and cross-sectional studies oriented toward description of in human aging processes. The scientific goals include identifying age differences among individuals and changes in individuals over time; to characterize transitions from normal to pathological aging; to determine the relative contribution of aging, disease processes, cohort effects and secular effects; to expand scientific understanding about predictors and risk factors for specific diseases and for other end points; and where possible to explore mechanisms for normal and/or pathological changes. The Chief, LSS, is the Director, BLSA; LSS staff administer and manage the BLSA operations and the clinical evaluations of the research volunteers. LSS scientists also conduct research with the BLSA. The BLSA Executive Committee, an internally comprised committee of GRC scientists and the Director, BLSA, is responsible for oversight of BLSA operations and research. The total BLSA population as of 9/1/99 includes 1296 participants (648 women; 648 men), 569 inactive (251 women; 318 men), and 815 deceased (117 women; 698 men). At present 16% of all active men and 22% of the active women are African-American. Overall, over 25% of the active participants are members of a minority group. Between 10/1/98 and 9/13/99, 535 participants visited the GRC for the regular 2- to 2-1/2-day visit. This includes 180 new particiants and 33 formerly inactive participants. A high priority is systematic follow-up and re-enrollment efforts directed at inactive participants, and attrition prevention strategies targeting currently active participants. Sarah Holmes, Ph.D., Project Director for follow- up, is in charge of this aspect of the program. The new transportation program for non-local particiants implemented this year is successful and cost effective. Of the 815 deceased participants, we have on file death certificates for 92%, physician and/or hospital reports for 38%, and autopsy reports for 19%. - Human Subjects